Chlorination of synthetic polymers



liters of oxygen per hour per liter of solution undergoing treatment.

Chlorine is preferably supplied at a rate of about volumes for each 100 volumes of air supplied. If the chlorine is supplied in quantities greater than about 22 volumes per 100 volumes of air, the reaction takes on the nature of a chlorination, rather than the preliminary chlorine-and-air treatment of this invention, and the products do not have the excellent properties characteristic of those produced in accordance with this invention. On the other hand, if the chlorine is supplied in amounts less than about 2.5 volumes per 100 volumes of air, the products are dark in color and are otherwise unsuitable. In case oxygen or some oxygen-bearing gas other than air is employed, it is understood that the amount of chlorine should be increased or decreased in proportion to the ratio of concentration of oxygen in the selected oxygen-bearing gas to the concentration of oxygen in air. On this basis, therefore, chlorine should be supplied at a rate of at least about 8 volumes of chlorine per 100 volumes of oxygen, the preferred ratio being about 50 volumes of chlorine per 100 volumes of oxygen, and

the maximum ratio being about 75 volumes of chlorine per 100 volumes of oxygen.

In general, any light source a substantial portion of the spectrum of which lies in the ultraviolet region, may be used to irradiate the reaction mass during the chlorine-and-air treatment. For instance, an incandescent bulb, particularly if ofuthe phot'oflood type, may be used in the practice of this invention. However, best results are obtained with somewhat shorter wavelengths, such for instance as are produced by electric discharge through mercury vapor.

The temperature of the reaction mass during I the preliminary chlorine-and-air treatment should preferably be kept in the range 1040 C. Higher temperatures, up to about 80 C. may be used, but increase the diiiiculty of control and also result in increased entrainment of the solvent by the treating gases. Lower temperatures result in an undesirably slow reaction.

Coming now to the duration of the preliminary chlorine-and-air treatment, under the preferred conditions above outlined, the treatment will have progressed to the desired degree within 2 or 3 hours. One of the effects of the pretreatment appears to be a molecular disaggregation,.which is reflected in a progressively decreasing viscosity of the batch being processed. Observation of this viscosity will inform the operator of the extent to which the treatment has proceeded: Assuming that the solution being treated originally contained 2% of rubber, the solvent being carbon tetrachloride, a satisfactory degree of pretreatment will usually have been attained when the viscosity of the solution falls to between about 4 centipoises and about 1 centipoise. Variation of the viscosity to which the batch is reduced provides a tool for the control of the properties of the final product, particularly the solution viscosity of the final product. This is a feature of some interest, and illustrates one difference in the behavior of synthetic elastomers-as compared to natural rubberupon chlorination. Natural rubber undergoes a considerable disaggrega tion and reduction of viscosity upon chlorination,

whereas the synthetic rubbers are not greatly altered in this respect by simple chlorination. The irradiated chlorine-and-air treatment of this invention does, however, efiect a marked decrease in viscosity of the synthetic polymer,

which decrease is carried, with but little further change, into the final chlorinated product.

The chlorination step subsequent to the chlorine-air-ultra-violet treatment may be carried out in accordance with any procedures usual in the art of chlorinating rubber or synthetic rubher-like polymers. Preferably, the pretreated rubber, in solution in an inert solvent, is initially chlorinated by mere contact of the solution with gaseous chlorine. The mass will quite readily absorb the chlorine up to a certain point, which will be designated the limit of spontaneous chlorination. At this point it will be preferred to irradiate the reaction mass with ultra-violet light of the type previously described, during further chlorination. The chlorination, whether or not conducted under irradiation during the final stages, should be carried out to substantially complete saturation of the isoprene polymer.

The products of this invention are substantially identical in properties and behavior with the chlorinated natural rubbers, being readily soluble in oxygenated solvents to give fluid solu tions having a high tolerance for hydrocarbon solvents. The products are compatible with alkyd and other resins with which the chlorinatied natural rubbers are ordinarily formulated. The products produced in accordance with'thi's invention form hard, clear and transparent films having excellent resistance to actinic and chemical deterioration. They may be used in place of chlorinated natural rubber in paints, varnishes, enamels, adhesives (particularly for bonding rub her and other elastomers to metal) packaging films and the like. In general, they provide complete and exact replacements for chlorinated natural rubber in any of its usual applications.

With the foregoing general discussion in mind, there is given herewith a detailed formal example of the practice of this invention.

EXAMPLE The apparatus employed in this example comprised a 2-liter Pyrex glass cylinder 4'7 cm. tall and 8 cm. in diameter, the walls being 2 mm. thick. A 7 mm. Pyrex glass delivery tube extended down from the top to the bottom of the cylinder. The top of the delivery tube was provided wi*h a T connection, to one branch of which was supplied air and to the other of which-was supplied chlorine. Flowmeters were provided in each branch to measure the rate of flow of the respective gases. A quartz tube mercury vapor lamp was setup facing the cylinder, the axis of the lamp reflector being parallel with the axis of the cylinder, and the burner being 20 cm. from the nearest point on the cylinder. A series of runs was made with the aboveapparatus, using' difierentrates of flow of chlorine and air through the delivery tube, different concentrations of isoprene polymer, etc., as set forth fully hereinafter in Table I. i

In each run there was employed a polymerized isoprene (GR.SX-ll6) whch had been milled for 10 minutes, the milled polymer being made up into a solution, in carbon tetrachloride, of concentration selected for the particular run. 2500 grams of this solution were placed in the cylinder, the ultra-violet lam") turned on, and chlorine and air,

- at rates selected for that particular run, were bubbled into the mass through the delivery tube to provide the air-chlorine ultraviolet pretreatment of this invention. This pretreatment was carried on for a duration of time selected forthe run. At the-conclusion otthe pretreatment, the

--chlorination the solution wasablown .withriair; .to z remove chlorinaceous.gases,.. the;chlorinatedprod- Quot -was precipitated '.by additionzo'fv thessolultion to methanol, and.the.precipitatedrproduotzwashed with imethanol: and dried.

AThe' followingxproperies. of: processed materials ewerei determined inx-each. run.

i1); Theyiscosity, .in. centipoisesiof the" solution 1. libeforenthe. pretreatment withjohlorine and the case of 2%rs'olutionsi."thisv value 'rang edlfrom'j 22 to 40 centipoises; 5i2) The viscosity,. in centipoisespf 'theiisolutio'n fljafterithe pretreatment "(Table "SI, columns I headed .fBatch Viscosity).

.(3) The viscosity, in centipoises '0f.a"20'%' toluene {solution of the final chlorinated prod ct at 25 C. .(TablefI, columnheaded' Viscosity (cps. of.2O toluene solution at 259,0) ..('.4)"1The percentage of "chlorine in the'finalproduct'(oolumnl headed f%1fCl). .15) ..'Ihejdilution ratio,,i. e., the volume .of, mineral om; al-though insome runs the -;lamp;:1.vas:-:left;:ofi uringithe earlystages. l Atthe conclusiorrofthe 6 wimasaflowedr..ontcraaglass plate-r and-the-resultant film dried at roomitemperature. :Ifhe clarity, hardness and general; qualityo the .iidriedgfilmxiwas;subjectively: ratedsbylthei opxatonrwithra.wiewiltofiits use; as an; industrial ni'sh.:.coating. LThese-ratings .areg setz-outrin Tablezl; i-column' headed:SGompatibility. with nalkydsz ('7)" Thelfcolol vrating;of. Table I isjzthescolorlof :theypreoipitated. and; driedgproduct. i fFromianjinspection of Table I: it :willrbe; seen .1 temiengthatthe ratio of chlorine to airv should :not'be permitted totrise' above about 15270; ire about2 l volumes per1100 volumesof' air; asunder ;f.'the"se.. conditions, chlorination, rather than the phionn airLIiretreatment of this invention be ins Ytake .place,: 'thei product is poor in compatibility. andstability. Likewise (item '1.6)-;fthe gentirejomissionof chlorine results in' a product ,wh'ich'iflisdark colored, unstable and otherwise wor'thless.""'Best results were obtained (itemsfl3, .4,..l3715, and 22-245) using about 7 volumes of. air I.per .volume ofjchlorine. It will be notedthat'the (compatibility bf the final product with alkyd'resins was impaired when the air was supplied at arate of. lessjthan about liters per hour per lite'rz'of .splutiori'treatd.

ggg sjg :1. Chlorination 'Q-ffropertiesjoithe final product T Initial 'Final' "viscosity i 5 l Gone. Batch g 4 Per od Period ;;;(cps. of T, -,Comnat1- I I 5 .P m 4 f"Time ,Y P witho ut with .5202, .Q bility Stabil- 1 Run (111) F 3 *U-ltra- Ultra- -tolue11e went --With 'ity =-'No. 5965? aviolet -.vi0let solmzat "C1" .A'lkyds .(hou.rs) *(horus); (3.).

2 70 15 4 12.0 omitt'ed 2.0 =10 66.2 1:434 'good .poor i light 1. -"Omi tt.ed 4.0 67.0 J60; Wad-Th ns--- .do. 2 ":10" 4 ":i'2.2' '-Omitted 20 10 s4.s :54 ';do "good "Omitted as 10 55 .s 1.60 ldo do 21 Omitted "2:5- 10 ere :50 'Ld0; fair... -51 a: Omitted 4.5 8 1:66.7 60 silkingr good f16 3 4' F721 Omitted 2:0 i 11 63.4 5 :70 Tgood do w -7, wOmitted 40. 10 5.04.8 -44 .fa'zfair-.- -8,- *3 4 24 Omitted 1 .5 ns 25 :52- good Omitted 3.5 1 .518 4.6 52 .do= 10 i 5 4 .24 Omitted 2. s 65.8 ";do 11' N v Omitted .4. A... 8 ..do 5:12 10 1.3 3.9 ;Omitt'ed" 2. 739 1 wean :13: 2.0 2.9 Omitted 2. 20 1.62. 0.. 14. 25 j 2.5 Omitted 2. p :13 #047 15' 0 .225 4.0 Qmitted 2. ..18 623; .16; 5 0 2 0 i: "T18" FY62. 47. .'0' 5.0 2:0 "T10 ."5' *15 e 2 18 5 2.0 1.9 a 41.5 25 ..l8 61.9; .19. yrs 5 *18 "626 20 3 2.5 T 1.8 Y 75 .25" 15 61.6 5.21; 3 70 10 4.0 a 8.0 1.0 5 20 63.3 22 6.0 8.0 .o 5 18 63.3 23 4 l 70 10 8.0 8.0 Omitted 3. is 62.3 24

spirits which can be added per unit volume of a 5% toluene solution of the final product, without impairing the clarity thereof. (6) The compatibility of the final product with alkyd resins. This property was determined be chlorinated to yieldproducts substantially by making up a toluene solution ;containing identical with chlorinated natural rubber. The 8% of the product and 22% of a medium oil products produced in accordance with this inlength, fast drying, drying-oil modified glypvention may be used in paints, varnishes, adhetal resin having a viscosity of W-Y on the sives, packaging and other films, and for any Gardner-Holdt bubble viscosimeter, a minother applications where the chlorinated natural imum of 30% phthalic anhydride content and rubbers have heretofore been used. The process an acid number from 3 to 7. This solution 5 may be carried out expeditiously in relatively From the foregoing general discussion and detailed specific examples, it will be apparent that this invention provides a means whereby the synthetic polymers and copolymers of isoprene may simple low pressure apparatus, and presents no difficulties of control.

What is claimed is:

'1. Process which comprises forming a solution of a substance selected from the group consisting of synthetic polymers of 'isoprene and' copolymers thereof with up to 25% of unsaturated compounds copolymerizable therewith, contacting the solution with a gaseous mixture containing oxygen and from about 8 to about 75 volumes of chlorine per 100 volumes of oxygen, simultaneously irradiating the solution with ultraviolet light, and thereafter chlorinating the selected substance with gaseous chlorine. 2. Process which comprises forming a solution of a synthetic polymer of isoprene, contracting the solution with a gaseous mixture containing oxygen and from about 8 to about 75 volumes of chlorine per 100 volumes of oxygen, simultaneously irradiating the solution with ultraviolet light and thereafter chlorinating the synthetic polymer with gaseous chlorine.

3. Process which comprises forming a solution of a substance selected from the group consisting of synthetic polymers of isoprene and copolymers thereof with up to 25% of unsaturated compounds copolymerizable therewith, contacting the solution with a gaseous mixture containing oxygen and from about 8 to about 75 volumes of chlorine per 100 volumes of oxygen, the mixture being supplied at a rate such as to furnish at least 6 liters of oxygen per liter of solution per hour, simultaneously irradiating the solution with ultraviolet light, and thereafter chlorinating the selected substance with gaseous chlorine.

4. Process which comprises forming a solution of a substance selected from the group consisting of synthetic polymers of isoprene and copolymers thereof with up to 25% of unsaturated compounds copolymerizable therewith, contacting the solution with a gaseous mixture containing oxygen and about 50 volumes of chlorine per 100 volumes of oxygen, the mixture being supplied at such a rate as to furnish at least 6 liters of oxygen per liter of solution per hour, simultaneously irradiating the solution with ultraviolet light, and thereafter chlorinating the selected substance with gaseous chlorine.

5. Process which comprises forming a solution of a substance selected from the group consisting of synthetic polymers of isoprene and copolymers thereof with up to 25% of unsaturated compounds copclymerizable therewith, contacting the solution with a mixture of air with from about 2.5 to about 22 volumes of chlorine per 100 volumes of air, simultaneously irradiating the solution with ultraviolet light, and thereafter chlorinating the selected substance with gaseous chlorine.

6; Process which comprises forming a solution of a substance selected from the group consisting of synthetic polymers of isoprene and copolymers thereof'with up to 25% of unsaturated compounds copolymerizable therewith, contacting the-solution with a mixture of air with about 15 volumes of chlorine per volumes of air, simultaneously irradiating the solution with ultraviolet lightpand thereafter chlorinating the selected substance with gaseous chlorine.

7. Process which comprises forming a solution of a substance selected from the group consisting of synthetic polymers of isoprene and copolymers thereof with up to 25% of unsaturated compounds copolymerizable therewith, contacting the solution with a mixture of air with about 15 volumes of chlorine per 100 volumes of air, the mixture being supplied at a rate such as to furnish about 45 liters of air per hour per liter of solution, simultaneously irradiating the solution with ultraviolet light, and thereafter chlorinating the selected substance with gaseous chlorine.

8. Process which comprises forming a solution of a synthetic polymer of isoprene, contacting the solution with a mixture of air with about 15 volumes of chlorine per 100 volumes of air, the mixture bein supplied at a rate suchas to furnish about 45 liters of air per hour per liter of solution, simultaneously irradiating the solution with ultraviolet light, and thereafter chlorinating the synthetic polymer with gaseous chlorine.

9. Process which comprises forming a solution of a synthetic polymer of isoprene, contacting the solution with a mixture of air with about 15 volumes of chlorine per 100 volumes of air, the mixture being supplied at a rate such as to furnish about 45 liters of air per hour per liter of solution, simultaneously irradiating the solution with ultraviolet light, and thereafter chlorinating 'said polymer with gaseous chlorine in the absence of ultraviolet light until the cessation of rapid and spontaneous absorption of chlorine by the polymenand finally continuing the chlorination with gaseous chlorine while exposing the polymer to ultraviolet light.

, ALBERT BARTOVICS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 7 Name Date 2,181,158 Sparks et al Nov. 28, 1939 2,222,345 Blomer et a1. Nov. 19, 1940 2,291,574 Gleason et al. July 28, 1942 2,292,737 Blomer et al Aug. 11, 1942 2,301,926 Blomer et al. Nov. 17, 1942 2,345,507 Smith Mar. 28, 1944 

1. PROCESS WHICH COMPRISES FORMING A SOLUTION OF A SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF SYNTHETIC POLYMERS OF ISOPRENE AND COPOLYMERS THEREOF WITH UP TO 25% OF UNSATURATED COMPOUNDS COPOLYMERIZABLE THEREWITH, CONTACTING THE SOLUTION WITH A GASEOUS MIXTURE CONTAINING OXYGEN AND FROM ABOUT 8 TO ABOUT 75 VOLUMES OF CHLORINE PER 100 VOLUMES OF OXYGEN, SIMULTANEOUSLY IRRADIATING THE SOLUTION THE SELECTED SUBSTANCE WITH GASEOUS CHLORINE. 